Wikipedia:Content policy in a nutshell
Claims should come from published sources that can be verified by other Wikipedia editors.
Verifiable claims should be based on references released by established experts and/or publishers with editorial oversight that have a reputation for fact-checking and accuracy.
Citing verifiable reliable sources is necessary for editors to verify the claims and assess the reliability of the references.
Wikipedia articles should present the claims and opinions appearing in the published body of reliable sources, in proportion to their prominence.
Claims must be verifiable in reliable references; consequently, editors may not insert their opinion or analysis of a subject into Wikipedia articles, explicitly or through presentation.
Wikipedia articles require enough reliable independent sources to justify a complete article. There are subjects that possess enough sources to build some kind of article, but what Wikipedia is not still applies.